Cable television networks such as those provided by Comcast Cable Communications, Inc., of Philadelphia, Pa., Cox Communications of Atlanta Ga., Time-Warner Cable, of Marietta Ga., Continental Cablevision, Inc., of Boston Mass., and others, provide cable television services to a large number of subscribers over a large geographical area. The cable television networks are typically interconnected by cables such as coaxial cables or a Hybrid Fiber/Coaxial (“HFC”) cable system that have data rates of about 10 Mega-bits-per-second (“Mbps”) to 30+ Mbps.
The Internet, a world-wide-network of interconnected computers, provides multi-media content including audio, video, graphics and text that require a large bandwidth for downloading and viewing. Most Internet Service Providers (“ISPs”) allow customers to connect to the Internet via a serial telephone line from a Public Switched Telephone Network (“PSTN”) at data rates including 14,400 bps, 28,800 bps, 33,600 bps, 56,000 bps and others that are much slower than the about 10 Mbps to 30+ Mbps available on a coaxial cable or HFC cable system on a cable television network.
With the explosive growth of the Internet, many customers have desired to use the larger bandwidth of a cable television network to connect to the Internet and other computer networks. Cable modems, such as those provided by 3Com Corporation of Santa Clara, Calif., Motorola Corporation of Arlington Heights, Ill., Cisco Corporation of San Jose, Calif., Scientific-Atlanta, of Norcross, Ga. and others offer customers higher-speed connectivity to the Internet, an intranet, Local Area Networks (“LANs”) and other computer networks via cable television networks.
These cable modems currently support a data connection to the Internet and other computer networks via a cable television network with a data rate of up to 30+ Mbps, which is a much larger data rate than can be supported by a modem used over a serial telephone line.
Many cable television networks provide bi-directional cable systems, in which data is sent “downstream”, from a “headend” to a customer, as well as “upstream”, from the customer back to the headend. The cable system headend is a central location in the cable television network and, further, is responsible for sending cable signals in the downstream direction and receiving cable signals in the upstream direction. An exemplary data-over-cable system with RF return typically includes customer premises equipment, a cable modem, a cable modem termination system, a cable television network, and a data network such as the Internet.
Some cable television networks provide only uni-directional cable systems, supporting only a “downstream” data path, which provides a path for flow of data from a cable system headend to a customer. In such a system, a return data path, an upstream data path, may be provided via a telephone network, such as a public switched telephone network provided by AT&T and others. A cable television system with an upstream connection to a telephony network is typically called a “data-over-cable system with telephony return.”
An exemplary data-over-cable system with a telephony return typically includes customer premise equipment (“CPE”) entities (such as a customer computer or a Voice over Internet Protocol (“VoIP”) device), a cable modem, a cable modem termination system, a cable television network, a public switched telephone network, a telephony remote access concentrator, and a data network (e.g., the Internet). The cable modem termination system and the telephony remote access concentrator combined are called a telephony return termination system.
If the customer premises equipment entity comprises a telephone or a device capable of sending and receiving video or voice signals, the cable modem has to be capable of sending and receiving such signals. In such cases the cable modem typically comprises an internal media terminal adapter, which provides a network interface functionality that accepts analog voice inputs or video signals and generates IP packets using the Real Time Transport protocol, for instance.
In a bi-directional cable system, when the cable modem termination system receives data packets from the data network, the cable modem termination system transmits received data packets downstream via the cable television network to a cable modem attached to the customer premises equipment entity. The customer premises equipment entity sends response data packets to the cable modem, which sends the response data packets upstream via the cable network. The cable modem termination system sends the response data packets back to the appropriate host on the data network.
As the popularity of the wireless communication increases, many data-over-cable system providers employ wireless transmission over traditional upstream and downstream paths. A wireless broadband modem service architecture, such as a Multichannel Multipoint Distribution Services (“MMDS”) architecture, is a fixed wireless access solution being employed by service providers to offer broadband data and voice access to their customers. The wireless broadband architecture typically includes head-end equipment and reception equipment. The head-end equipment may include satellite signal reception equipment, radio transmitters, broadcast equipment, and a transmission antenna. The reception equipment at each subscriber location may include an antenna, a frequency conversion device and a set-top device. Signals for Multichannel Multipoint Distribution Services broadcast at the transmitter site originate from a variety of sources. Satellite, terrestrial and cable delivered programs, in addition to local baseband services, comprise the material to be delivered over the Multichannel Multipoint Distribution Services.
Typical data-over-cable systems operate according to a set of specifications, one of which is the Data-Over-Cable Service Interface Specification (“DOCSIS”), published by Cable Television Laboratories. The Data-Over-Cable Service Interface Specification is an IP centric point to multi-point standard that was developed for broadband Internet access applications over cable television networks. As such, the standard is designed to support existing and later developed IP based network services. The DOCSIS specification is an excellent resource when employed, for example, with network and data link protocols, Quality of Service, convergence, synchronization, registration, encryption, or privacy related implementations. However, because the DOCSIS was designed for cable television systems, it is inadequate to address some unique characteristics and requirements of other types of systems such as the wireless system. In wireless systems, the upstream performance differs from a typical upstream path of a cable system. Some of the upstream performance characteristics of the upstream wireless channel include, for example, a limited carrier to noise ratio, an interference from co-channels and reused frequencies, a carrier frequency offset between a headend modulator and a customer premises entity demodulator, a fading receiving power level at the base station, or a high dynamic range at a base station receiver.
As is known in the art, employing the Orthogonal Frequency Division Multiplexing (“OFDM”) modulation on downstream channels of a cable television system can enhance a downstream channel performance. The Orthogonal Frequency Division Multiplexing modulation splits a data stream into a plurality of radio frequency channels, each of which is sent over a subcarrier frequency, while a signal-to-noise ratio is monitored to ensure maximum performance. However, in order to match the performance of the OFDM downstream, the performance of an upstream path should be enhanced. One of the solutions that adds the frequency diversity on an upstream channel involves having antenna diversity on a client device. However, such an embodiment is not efficient and very expensive since having the antenna diversity on a client device can double the cost of this equipment in every home deployment.
Thus, it is desirable to develop standard, reliable, efficient, and preferably integrated into the existing cable modem infrastructure, systems and methods for adding robustness to an upstream and downstream path for a fixed wireless, cable or satellite system.